Foaming of Set-Delayed Cement Compositions Comprising Pumice and Hydrated Lime

ABSTRACT

A variety of methods and compositions are disclosed, including, in one embodiment a method a cementing in a subterranean formation comprising: providing a set-delayed cement composition comprising water, pumice, hydrated lime, and a set retarder; foaming the set-delayed cement composition; activating the set-delayed cement composition; introducing the set-delayed cement composition into a subterranean formation; and allowing the set-delayed cement composition to set in the subterranean formation. Additional methods, foamed set-delayed cement composition, and systems for cementing are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/032,734, filed on Sep. 20, 2013, which is a continuation-in-part ofU.S. patent application Ser. No. 13/417,001, filed on Mar. 9, 2012,titled “Set-Delayed Cement Compositions Comprising Pumice and AssociatedMethods,” (now U.S. Pat. No. 8,851,173), and also claims priority toU.S. Provisional Patent Application No. 61/875,410, filed on Sep. 9,2013, titled “Foaming of Set-Delayed Cement Compositions ComprisingPumice and Hydrated Lime” the entire disclosures of which areincorporated herein by reference.

BACKGROUND

Cement compositions may be used in a variety of subterranean operations.For example, in subterranean well construction, a pipe string (e.g.,casing, liners, expandable tubulars, etc.) may be run into a wellboreand cemented in place. The process of cementing the pipe string in placeis commonly referred to as “primary cementing.” In a typical primarycementing method, a cement composition may be pumped into an annulusbetween the walls of the wellbore and the exterior surface of the pipestring disposed therein. The cement composition may set in the annularspace, thereby forming an annular sheath of hardened, substantiallyimpermeable cement (i.e., a cement sheath) that may support and positionthe pipe string in the wellbore and may bond the exterior surface of thepipe string to the subterranean formation. Among other things, thecement sheath surrounding the pipe string functions to prevent themigration of fluids in the annulus, as well as protecting the pipestring from corrosion. Cement compositions also may be used in remedialcementing methods, for example, to seal cracks or holes in pipe stringsor cement sheaths, to seal highly permeable formation zones orfractures, to place a cement plug, and the like.

A broad variety of cement compositions have been used in subterraneancementing operations. In some instances, set-delayed cement compositionshave been used. Set-delayed cement compositions are characterized byremaining in a pumpable fluid state for at least about one day (e.g., atleast about 7 days, about 2 weeks, about 2 years or more) at roomtemperature (e.g., about 80° F.) in quiescent storage. When desired foruse, the set-delayed cement compositions should be capable of beingactivated whereby reasonable compressive strengths are developed. Forexample, a cement set accelerator may be added to a set-delayed cementcomposition whereby the composition sets into a hardened mass. Amongother things, the set-delayed cement composition may be suitable for usein wellbore applications, for example, where it is desired to preparethe cement composition in advance. This may allow, for example, thecement composition to be stored prior to its use. In addition, this mayallow, for example, the cement composition to be prepared at aconvenient location and then transported to the job site. Accordingly,capital expenditures may be reduced due to a reduction in the need foron-site bulk storage and mixing equipment. This may be particularlyuseful for offshore cementing operations where space onboard the vesselsmay be limited.

While set-delayed cement compositions have been developed heretofore,challenges exist with their successful use in subterranean cementingoperations. For example, set-delayed cement compositions prepared withPortland cement may have undesired gelation issues which can limit theiruse and effectiveness in cementing operations. Other set-delayedcompositions that have been developed, for example, those comprisinghydrated lime and quartz, may be effective in some operations but mayhave limited use at lower temperatures as they may not developsufficient compressive strength when used in subterranean formationshaving lower bottom hole static temperatures.

BRIEF DESCRIPTION OF THE DRAWINGS

These drawings illustrate certain aspects of some of the embodiments ofthe present method, and should not be used to limit or define themethod.

FIG. 1 illustrates a system for preparation and delivery of aset-delayed cement composition to a wellbore in accordance with certainembodiments.

FIG. 2A illustrates surface equipment that may be used in placement of aset-delayed cement composition in a wellbore in accordance with certainembodiments.

FIG. 2B illustrates placement of a set-delayed cement composition into awellbore annulus in accordance with certain embodiments.

DESCRIPTION OF PREFERRED EMBODIMENTS

The example embodiments relate to subterranean cementing operations and,more particularly, in certain embodiments, to set-delayed cementcompositions and methods of using set-delayed cement compositions insubterranean formations.

Embodiments of the set-delayed cement compositions may generallycomprise water, pumice, hydrated lime, and a set retarder. Optionally,the set-delayed cement compositions may further comprise a dispersant.Embodiments of the set-delayed cement compositions may be foamed.Advantageously, embodiments of the set-delayed cement compositions maybe capable of remaining in a pumpable fluid state for an extended periodof time. For example, the set-delayed cement compositions may remain ina pumpable fluid state for at least about 1 day, about 2 weeks, about 2years, or longer. Advantageously, the set-delayed cement compositionsmay develop reasonable compressive strengths after activation atrelatively low temperatures. While the set-delayed cement compositionsmay be suitable for a number of subterranean cementing operations, theymay be particularly suitable for use in subterranean formations havingrelatively low bottom hole static temperatures, e.g., temperatures lessthan about 200° F. or ranging from about 100° F. to about 200° F. Inalternative embodiments, the set-delayed cement compositions may be usedin subterranean formations having bottom hole static temperatures up to450° F. or higher.

The water used in embodiments of the set-delayed cement compositions maybe from any source provided that it does not contain an excess ofcompounds that may undesirably affect other components in theset-delayed cement compositions. For example, a set-delayed cementcomposition may comprise fresh water or salt water. Salt water generallymay include one or more dissolved salts therein and may be saturated orunsaturated as desired for a particular application. Seawater or brinesmay be suitable for use in embodiments. Further, the water may bepresent in an amount sufficient to form a pumpable slurry. In certainembodiments, the water may be present in the set-delayed cementcomposition in an amount in the range of from about 33% to about 200% byweight of the pumice. In certain embodiments, the water may be presentin the set-delayed cement compositions in an amount in the range of fromabout 35% to about 70% by weight of the pumice. One of ordinary skill inthe art with the benefit of this disclosure will recognize theappropriate amount of water for a chosen application.

Embodiments of the set-delayed cement compositions may comprise pumice.Generally, pumice is a volcanic rock that can exhibit cementitiousproperties in that it may set and harden in the presence of hydratedlime and water. The pumice may also be ground. Generally, the pumice mayhave any particle size distribution as desired for a particularapplication. In certain embodiments, the pumice may have a mean particlesize in a range of from about 1 micron to about 200 microns. The meanparticle size corresponds to d50 values as measured by particle sizeanalyzers such as those manufactured by Malvern Instruments,Worcestershire, United Kingdom. In specific embodiments, the pumice mayhave a mean particle size in a range of from about 1 micron to about 200microns, from about 5 microns to about 100 microns, or from about 10microns to about 50 microns. In one particular embodiment, the pumicemay have a mean particle size of less than about 15 microns. An exampleof a suitable pumice is available from Hess Pumice Products, Inc.,Malad, Id., as DS-325 lightweight aggregate, having a particle size ofless than about 15 microns. It should be appreciated that particle sizestoo small may have mixability problems while particle sizes too largemay not be effectively suspended in the compositions. One of ordinaryskill in the art, with the benefit of this disclosure, should be able toselect a particle size for the pumice suitable for a chosen application.

Embodiments of the set-delayed cement compositions may comprise hydratedlime. As used herein, the term “hydrated lime” will be understood tomean calcium hydroxide. In some embodiments, the hydrated lime may beprovided as quicklime (calcium oxide) which hydrates when mixed withwater to form the hydrated lime. The hydrated lime may be included inembodiments of the set-delayed cement compositions, for example, to forma hydraulic composition with the pumice. For example, the hydrated limemay be included in a pumice-to-hydrated-lime weight ratio of about 10:1to about 1:1 or 3:1 to about 5:1. Where present, the hydrated lime maybe included in the set-delayed cement compositions in an amount in therange of from about 10% to about 100% by weight of the pumice, forexample. In some embodiments, the hydrated lime may be present in anamount ranging between any of and/or including any of about 0%, about20%, about 40%, about 60%, about 80%, or about 100% by weight of thepumice. In some embodiments, the cementitious components present in theset-delayed cement composition may consist essentially of the pumice andthe hydrated lime. For example, the cementitious components mayprimarily comprise the pumice and the hydrated lime without anyadditional components (e.g., Portland cement, fly ash, slag cement) thathydraulically set in the presence of water. One of ordinary skill in theart, with the benefit of this disclosure, will recognize the appropriateamount of the hydrated lime to include for a chosen application.

Embodiments of the set-delayed cement compositions may comprise a setretarder. A broad variety of set retarders may be suitable for use inthe set-delayed cement compositions. For example, the set retarder maycomprise phosphonic acids, such as ethylenediamine tetra(methylenephosphonic acid), diethylenetriamine penta(methylene phosphonic acid),etc.; lignosulfonates, such as sodium lignosulfonate, calciumlignosulfonate, etc.; salts such as stannous sulfate, lead acetate,monobasic calcium phosphate, organic acids, such as citric acid,tartaric acid, etc.; cellulose derivatives such as hydroxyl ethylcellulose (HEC) and carboxymethyl hydroxyethyl cellulose (CMHEC);synthetic co- or ter-polymers comprising sulfonate and carboxylic acidgroups such as sulfonate-functionalized acrylamide-acrylic acidco-polymers; borate compounds such as alkali borates, sodium metaborate,sodium tetraborate, potassium pentaborate; derivatives thereof, ormixtures thereof. Examples of suitable set retarders include, amongothers, phosphonic acid derivatives. One example of a suitable setretarder is Micro Matrix® cement retarder, available from HalliburtonEnergy Services, Inc. Generally, the set retarder may be present in theset-delayed cement compositions in an amount sufficient to delay thesetting for a desired time. In some embodiments, the set retarder may bepresent in the set-delayed cement compositions in an amount in the rangeof from about 0.01% to about 10% by weight of the pumice. In specificembodiments, the set retarder may be present in an amount rangingbetween any of and/or including any of about 0.01%, about 0.1%, about1%, about 2%, about 4%, about 6%, about 8%, or about 10% by weight ofthe pumice. One of ordinary skill in the art, with the benefit of thisdisclosure, will recognize the appropriate amount of the set retarder toinclude for a chosen application.

As previously mentioned, embodiments of the set-delayed cementcompositions may optionally comprise a dispersant. Examples of suitabledispersants include, without limitation, sulfonated-formaldehyde-baseddispersants (e.g., sulfonated acetone formaldehyde condensate), examplesof which may include Daxad® 19 available from Geo Specialty Chemicals.Ambler, Pa. Other suitable dispersants may be polycarboxylated etherdispersants such as Liquiment® 5581F and Liquiment® 514L available fromBASF Corporation Houston, Tex.: or Ethacryl G available from Coatex.Genay. France. An additional example of a suitable commerciallyavailable dispersant is CFR™-3 dispersant, available from HalliburtonEnergy Services, Inc, Houston, Tex. Of particular importance in regardsto the examples that follow, is that the Liquiment® 514L dispersantcomprises 36% by weight of the polycarboxylated ether in water. While avariety of dispersants may be used in accordance with embodiments,polycarboxylated ether dispersants may be particularly suitable for usein some embodiments. Without being limited by theory, it is believedthat polycarboxylated ether dispersants may synergistically interactwith other components of the set-delayed cement composition. Forexample, it is believed that the polycarboxylated ether dispersants mayreact with certain set retarders (e.g., phosphonic acid derivatives)resulting in formation of a gel that suspends the pumice and hydratedlime in the composition for an extended period of time.

In some embodiments, the dispersant may be included in the set-delayedcement compositions in an amount in the range of from about 0.01% toabout 5% by weight of the pumice. In specific embodiments, thedispersant may be present in an amount ranging between any of and/orincluding any of about 0.01%, about 0.1%, 0.5%, about 1%, about 2%,about 3%, about 4%, or about 5% by weight of the pumice. One of ordinaryskill in the art, with the benefit of this disclosure, will recognizethe appropriate amount of the dispersant to include for a chosenapplication.

Embodiments of the set-delayed cement compositions may comprise amechanical property enhancing additive. Mechanical-property-enhancingadditives may be included in embodiments of the set-delayed compositionsto, for example, ensure adequate compressive strength and long-termstructural integrity. These properties can be affected by the strains,stresses, temperature, pressure, and impact effects from a subterraneanenvironment. Examples of mechanical property enhancing additives includefibers, such as graphitic carbon fibers, glass fibers, steel fibers,mineral fibers, silica fibers, polyester fibers, polyamide fibers, andpolyolefin fibers, among others. Specific examples of graphitic carbonfibers include fibers derived from polyacrylonitrile, rayon, andpetroleum pitch. Where used, the mechanical-property-enhancing additivesmay be present in an amount from about 0.01% to about 5% by weight ofthe pumice. In specific embodiments, the mechanical-property-enhancingadditives may be present in an amount ranging between any of and/orincluding any of about 0.01%, about 0.1%, 0.5%, about 1%, about 2%,about 3%, about 4%, or about 5% by weight of the pumice. One of ordinaryskill in the art, with the benefit of this disclosure, will recognizethe appropriate amount of the mechanical-property-enhancing additives toinclude for a chosen application.

Other additives suitable for use in subterranean cementing operationsalso may be included in embodiments of the set-delayed cementcompositions. Examples of such additives include, but are not limitedto, weighting agents, lightweight additives, gas-generating additives,lost-circulation materials, filtration-control additives,fluid-loss-control additives, defoaming agents, foaming agents,thixotropic additives, and combinations thereof. In embodiments, one ormore of these additives may be added to the set-delayed cementcomposition after storing but prior to placement of the set-delayedcement composition into a subterranean formation. A person havingordinary skill in the art, with the benefit of this disclosure, willreadily be able to determine the type and amount of additive useful fora particular application and desired result.

Those of ordinary skill in the art will appreciate that embodiments ofthe set-delayed cement compositions generally should have a densitysuitable for a particular application. By way of example, theset-delayed cement compositions may have a density in the range of fromabout 4 pounds per gallon (“lb/gal”) to about 20 lb/gal. In certainembodiments, the set-delayed cement compositions may have a density inthe range of from about 8 lb/gal to about 17 lb/gal. Embodiments of theset-delayed cement compositions may be foamed or unfoamed or maycomprise other means to reduce their densities, such as hollowmicrospheres, low-density elastic beads, or other density-reducingadditives known in the art. In embodiments, the density may be reducedafter storing the composition, but prior to placement in a subterraneanformation. Those of ordinary skill in the art, with the benefit of thisdisclosure, will recognize the appropriate density for a particularapplication.

As discussed above, embodiments of the set-delayed cement compositionsmay be foamed. Embodiments of the set-delayed cement compositions may befoamed to provide a lightweight composition that does not exertexcessive force on formations penetrated by the wellbore. In addition tobeing lightweight, a foamed composition may also improve the ability ofthe composition to maintain pressure and prevent the flow of formationfluids into and through the composition during its transition time.Foamed compositions may also be advantageous because they have low fluidloss properties, thus limiting loss of fluid circulation. Additionally,foamed compositions when set may also have a lower modulus of elasticitythan non-foamed compositions, which is often desirable as it enables theresultant set cement composition to resist stresses exerted on thecomposition in situ.

In particular embodiments, the set-delayed cement composition may befoamed at the well site. By way of example, the set-delayed cementcompositions may be foamed immediately prior to use. Embodiments may befoamed with a foaming additive and by entraining gas into theset-delayed cement compositions. In particular embodiments, the foamingadditive and gas may be introduced after combination of the compositionwith an activator. The set-delayed cement compositions may be foamed,for example, to provide a set-delayed cement composition with a reduceddensity.

The gas used for foaming the composition may be any suitable gas forfoaming, including, but not limited to: air, nitrogen, and combinationsthereof. Generally, the gas should be in an amount sufficient to formthe desired foam. Foaming additives may be included in embodiments to,for example, facilitate foaming and/or stabilize the resultant foamformed therewith.

In particular embodiments, the foaming additive may include a surfactantor combination of surfactants that reduce the surface tension of thewater. By way of example, the foaming agent may comprise an anionic,nonionic, amphoteric (including zwitterionic surfactants), cationicsurfactant, or mixtures thereof. Examples of suitable foaming additivesinclude, but are not limited to: betaines; anionic surfactants such ashydrolyzed keratin; amine oxides such as a alkyl or alkene dimethylamine oxides; cocoamidopropyl dimethylamine oxide; methyl estersulfonates; alkyl or alkene amidobetaines such as cocoamidopropylbetaine; alpha-olefin sulfonates; quaternary surfactants such astrimethyltallowammonium chloride and trimethylcocoammonium chloride; C8to C22 alkylethoxylate sulfates; and combinations thereof. Specificexamples of suitable foaming agents include mixtures of an ammonium saltof an alkyl ether sulfate, a cocoamidopropyl betaine surfactant, acocoamidopropyl dimethylamine oxide surfactant, sodium chloride, andwater; mixtures of an ammonium salt of an alkyl ether sulfatesurfactant, a cocoamidopropyl hydroxysultaine surfactant, acocoamidopropyl dimethylamine oxide surfactant, sodium chloride, andwater; mixtures of an ethoxylated alcohol ether sulfate surfactant, analkyl or alkene amidopropyl betaine surfactant, and an alkyl or alkenedimethylamine oxide surfactant; aqueous solutions of an alpha-olefinicsulfonate surfactant and a betaine surfactant; and combinations thereof.Examples of suitable foaming additives are ZONESEALANT™ 2000 agent andFoamer 1026™, both available from Halliburton Energy Services Inc.,Houston, Tex. Embodiments may be foamed within a foam quality range ofbetween about 5% to about 80% and, more particularly, from about 18% toabout 38%. As used herein, the term “foam quality” refers to the volumeof entrained gas and is defined by the following formula: FoamQuality=(Total Foam Volume−Liquid Volume)/Total Foam Volume.

As previously mentioned, the cement compositions may have a delayed setin that they remain in a pumpable fluid state for at least one day(e.g., at least about 1 day, about 2 weeks, about 2 years, or longer) atroom temperature in quiescent storage. For example, the set-delayedcement compositions may remain in a pumpable fluid state for a period oftime from about 1 day, about 2 weeks, about 2 years, or longer. In someembodiments, the set-delayed cement compositions may remain in apumpable fluid state for at least about 1 day, about 7 days, about 10days, about 20 days, about 30 days, about 40 days, about 50 days, about60 days, about 2 years, or longer. A fluid is considered to be in apumpable fluid state where the fluid has a consistency of less than 70Bearden units of consistency (“Be”), as measured on a high-temperaturehigh-pressure consistometer at room temperature (e.g., about 80° F.) inaccordance with the procedure for determining cement thickening timesset forth in API RP Practice 10B-2, Recommended Practice for TestingWell Cements, First Edition, July 2005.

When desired for use, embodiments of the set-delayed cement compositionsmay be activated (e.g., by combination with an activator) to thereby setinto a hardened mass. By way of example, embodiments of the set-delayedcement compositions may be activated to set to form a hardened mass in atune period in the range of from about 1 hour to about 12 hours. Forexample, embodiments of the set-delayed cement compositions may set toform a hardened mass in a time period ranging between any of and/orincluding any of about 1 day, about 2 days, about 4 days, about 6 days,about 8 days, about 10 days, or about 12 days.

In some embodiments, the set-delayed cement compositions may set to havea desirable compressive strength after activation. Compressive strengthis generally the capacity of a material or structure to withstandaxially directed pushing forces. The compressive strength may bemeasured at a specified time after the set-delayed cement compositionhas been activated and the resultant composition is maintained underspecific temperature and pressure controls. Compressive strength can bemeasured by either a destructive method or non-destructive method. Thedestructive method physically tests the strength of treatment fluidsamples at various points in time by crushing the samples in acompression-testing machine. The compressive strength is calculated fromthe failure load divided by the cross-sectional area resisting the loadand is reported in units of pound-force per square inch (psi).Non-destructive methods typically may employ an Ultrasonic CementAnalyzer (“UCA”), available from Fann Instrument Company, Houston, Tex.Compressive strengths may be determined in accordance with API RP 10B-2,Recommended Practice for Testing Well Cements, First Edition. July 2005.

By way of example, the set-delayed cement composition, may develop a24-hour compressive strength in the range of from about 50 psi to about5000 psi, alternatively, from about 100 psi to about 4500 psi, oralternatively from about 500 psi to about 4000 psi. In some embodiments,the set-delayed cement composition may develop a compressive strength in24 hours of at least about 50 psi, at least about 100 psi, at leastabout 500 psi, or more. In some embodiments, the compressive strengthvalues may be determined using destructive or non-destructive methods ata temperature ranging from 100° F. to 200° F.

Embodiments may include the addition of a cement set activator to theset-delayed cement compositions. Examples of suitable cement setactivators include, but are not limited to: amines such astriethanolamine, diethanolamine; silicates such as sodium silicate; zincformate; calcium acetate; Groups IA and IIA hydroxides such as sodiumhydroxide, magnesium hydroxide, and calcium hydroxide; monovalent saltssuch as sodium chloride; divalent salts such as calcium chloride;nanosilica (i.e., silica having a particle size of less than or equal toabout 100 nanometers); polyphosphates; and combinations thereof. In someembodiments, a combination of the polyphosphate and a monovalent saltmay be used for activation. The monovalent salt may be any salt thatdissociates to form a monovalent cation, such as sodium and potassiumsalts. Specific examples of suitable monovalent salts include potassiumsulfate, and sodium sulfate. A variety of different polyphosphates maybe used in combination with the monovalent salt for activation of theset-delayed cement compositions, including polymeric metaphosphatesalts, phosphate salts, and combinations thereof. Specific examples ofpolymeric metaphosphate salts that may be used include sodiumhexametaphosphate, sodium trimetaphosphate, sodium tetrametaphosphate,sodium pentametaphosphate, sodium heptametaphosphate, sodiumoctametaphosphate, and combinations thereof. A specific example of asuitable cement set activator comprises a combination of sodium sulfateand sodium hexametaphosphate. In particular embodiments, the activatormay be provided and added to the set-delayed cement composition as aliquid additive, for example, a liquid additive comprising a monovalentsalt, a polyphosphate, and optionally a dispersant.

The cement set activator should be added to embodiments of theset-delayed cement composition in an amount sufficient to activate theset-delayed cement composition to set into a hardened mass. In certainembodiments, the cement set activator may be added to the set-delayedcement composition in an amount in the range of about 1% to about 20% byweight of the pumice. In specific embodiments, the cement set activatormay be present in an amount ranging between any of and/or including anyof about 1%, about 5%, about 10%, about 15%, or about 20% by weight ofthe pumice. One of ordinary skill in the art, with the benefit of thisdisclosure, will recognize the appropriate amount of the cement setactivator to include for a chosen application.

As will be appreciated by those of ordinary skill in the art,embodiments of the set-delayed cement compositions may be used in avariety of subterranean operations, including primary and remedialcementing. In some embodiments, a set-delayed cement composition may beprovided that comprises water, pumice, hydrated lime, a set retarder,and optionally a dispersant. The set-delayed cement composition may beintroduced into a subterranean formation and allowed to set therein. Asused herein, introducing the set-delayed cement composition into asubterranean formation includes introduction into any portion of thesubterranean formation, including, without limitation, into a wellboredrilled into the subterranean formation, into a near wellbore regionsurrounding the wellbore, or into both. Embodiments may further includeactivation of the set-delayed cement composition. The activation of theset-delayed cement composition may comprise, for example, the additionof a cement set activator to the set-delayed cement composition.

In some embodiments, a set-delayed cement composition may be providedthat comprises water, pumice, hydrated lime, a set retarder, andoptionally a dispersant. The set-delayed cement composition may bestored, for example, in a vessel or other suitable container. Theset-delayed cement composition may be permitted to remain in storage fora desired time period. For example, the set-delayed cement compositionmay remain in storage for a time period of about 1 day, about 2 weeks,about 2 years, or longer. For example, the set-delayed cementcomposition may remain in storage for a time period of about 1 day,about 2 days, about 5 days, about 7 days, about 10 days, about 20 days,about 30 days, about 40 days, about 50 days, about 60 days, about 2years, or longer. In some embodiments, the set-delayed cementcomposition may remain in storage for a time period in a range of fromabout 1 day to about 2 years or longer. Thereafter, the set-delayedcement composition may be activated, for example, by addition of acement set activator, introduced into a subterranean formation, andallowed to set therein. Optionally, the set-delayed cement compositionmay be foamed prior to introduction into the subterranean formation.

In primary cementing embodiments, for example, embodiments of theset-delayed cement composition may be introduced into an annular spacebetween a conduit located in a wellbore and the walls of a wellbore(and/or a larger conduit in the wellbore), wherein the wellborepenetrates the subterranean formation. The set-delayed cementcomposition may be allowed to set in the annular space to form anannular sheath of hardened cement. The set-delayed cement compositionmay form a barrier that prevents the migration of fluids in thewellbore. The set-delayed cement composition may also, for example,support the conduit in the wellbore.

In remedial cementing embodiments, a set-delayed cement composition maybe used, for example, in squeeze-cementing operations or in theplacement of cement plugs. By way of example, the set-delayedcomposition may be placed in a wellbore to plug an opening such as avoid or crack that is in the formation, in a gravel pack, in theconduit, in the cement sheath, and/or between the cement sheath and theconduit (e.g., a microannulus).

An example embodiment comprises a method of cementing in a subterraneanformation comprising: providing a set-delayed cement compositioncomprising water, pumice, hydrated lime, and a set retarder; foaming theset-delayed cement composition; activating the foamed set-delayed cementcomposition; introducing the foamed set-delayed cement composition intoa subterranean formation; and allowing the foamed set-delayed cementcomposition to set in the subterranean formation.

An example embodiment comprises a foamed set-delayed cement compositioncomprising: water, pumice, hydrated lime, a foaming additive, entrainedgas, and a set retarder.

An example embodiment comprises a system for cementing comprising: aset-delayed cement composition comprising: water, pumice, hydrated lime,a set retarder, a foaming additive for foaming the set-delayed cementcomposition; a gas for foaming the set-delayed cement composition; and acement set activator for activation of the set-delayed cementcomposition.

Referring now to FIG. 1, preparation of a set-delayed cement compositionin accordance with example embodiments will now be described. FIG. 1illustrates a system 2 for preparation of a set-delayed cementcomposition and delivery to a wellbore in accordance with certainembodiments. As shown, the set-delayed cement composition may be mixedin mixing equipment 4, such as a jet mixer, re-circulating mixer, or abatch mixer, for example, and then pumped via pumping equipment 6 to thewellbore. In some embodiments, the mixing equipment 4 and the pumpingequipment 6 may be disposed on one or more cement trucks as will beapparent to those of ordinary skill in the art. In some embodiments, ajet mixer may be used, for example, to continuously mix thelime/settable material with the water as it is being pumped to thewellbore.

An example technique for placing a set-delayed cement composition into asubterranean formation will now be described with reference to FIGS. 2Aand 2B. FIG. 2A illustrates surface equipment 10 that may be used inplacement of a set-delayed cement composition in accordance with certainembodiments. It should be noted that while FIG. 2A generally depicts aland-based operation, those skilled in the art will readily recognizethat the principles described herein are equally applicable to subseaoperations that employ floating or sea-based platforms and rigs, withoutdeparting from the scope of the disclosure. As illustrated by FIG. 2A,the surface equipment 10 may include a cementing unit 12, which mayinclude one or more cement trucks. The cementing unit 12 may includemixing equipment 4 and pumping equipment 6 (e.g., FIG. 1) as will beapparent to those of ordinary skill in the art. The cementing unit 12may pump a set-delayed cement composition 14 through a feed pipe 16 andto a cementing head 18 which conveys the set-delayed cement composition14 downhole.

Turning now to FIG. 2B, the set-delayed cement composition 14 may beplaced into a subterranean formation 20 in accordance with exampleembodiments. As illustrated, a wellbore 22 may be drilled into thesubterranean formation 20. While wellbore 22 is shown extendinggenerally vertically into the subterranean formation 20, the principlesdescribed herein are also applicable to wellbores that extend at anangle through the subterranean formation 20, such as horizontal andslanted wellbores. As illustrated, the wellbore 22 comprises walls 24.In the illustrated embodiment, a surface casing 26 has been insertedinto the wellbore 22. The surface casing 26 may be cemented to the walls24 of the wellbore 22 by cement sheath 28. In the illustratedembodiment, one or more additional conduits (e.g., intermediate casing,production casing, liners, etc.), shown here as casing 30 may also bedisposed in the wellbore 22. As illustrated, there is a wellbore annulus32 formed between the casing 30 and the walls 24 of the wellbore 22and/or the surface casing 26. One or more centralizers 34 may beattached to the casing 30, for example, to centralize the casing 30 inthe wellbore 22 prior to and during the cementing operation.

With continued reference to FIG. 2B, the set-delayed cement composition14 may be pumped down the interior of the casing 30. The set-delayedcement composition 14 may be allowed to flow down the interior of thecasing 30 through the casing, shoe 42 at the bottom of the casing 30 andup around the casing 30 into the wellbore annulus 32. The set-delayedcement composition 14 may be allowed to set in the wellbore annulus 32,for example, to form a cement sheath that supports and positions thecasing 30 in the wellbore 22. While not illustrated, other techniquesmay also be utilized for introduction of the set-delayed cementcomposition 14. By way of example, reverse circulation techniques may beused that include introducing the set-delayed cement composition 14 intothe subterranean formation 20 by way of the wellbore annulus 32 insteadof through the casing 30.

As it is introduced, the set-delayed cement composition 14 may displaceother fluids 36, such as drilling fluids and/or spacer fluids that maybe present in the interior of the casing 30 and/or the wellbore annulus32. At least a portion of the displaced fluids 36 may exit the wellboreannulus 32 via a flow line 38 and be deposited, for example, in one ormore retention pits 40 (e.g., a mud pit), as shown on FIG. 2A. Referringagain to FIG. 2B, a bottom plug 44 may be introduced into the wellbore22 ahead of the set-delayed cement composition 14, for example, toseparate the set-delayed cement composition 14 from the fluids 36 thatmay be inside the casing 30 prior to cementing. After the bottom plug 44reaches the landing collar 46, a diaphragm or other suitable deviceshould rupture to allow the set-delayed cement composition 14 throughthe bottom plug 44. In FIG. 2B, the bottom plug 44 is shown on thelanding collar 46. In the illustrated embodiment, a top plug 48 may beintroduced into the wellbore 22 behind the set-delayed cementcomposition 14. The top plug 48 may separate the set-delayed cementcomposition 14 from a displacement fluid 50 and also push theset-delayed cement composition 14 through the bottom plug 44.

The exemplary set-delayed cement compositions disclosed herein maydirectly or indirectly affect one or more components or pieces ofequipment associated with the preparation, delivery, recapture,recycling, reuse, and/or disposal of the disclosed set-delayed cementcompositions. For example, the disclosed set-delayed cement compositionsmay directly or indirectly affect one or more mixers, related mixingequipment, mud pits, storage facilities or units, compositionseparators, heat exchangers, sensors, gauges, pumps, compressors, andthe like used generate, store, monitor, regulate, and/or recondition theexemplary set-delayed cement compositions. The disclosed set-delayedcement compositions may also directly or indirectly affect any transportor delivery equipment used to convey the set-delayed cement compositionsto a well site or downhole such as, for example, any transport vessels,conduits, pipelines, trucks, tubulars, and/or pipes used tocompositionally move the set-delayed cement compositions from onelocation to another, any pumps, compressors, or motors (e.g., topside ordownhole) used to drive the set-delayed cement compositions into motion,any valves or related joints used to regulate the pressure or flow rateof the set-delayed cement compositions, and any sensors (i.e., pressureand temperature), gauges, and/or combinations thereof, and the like. Thedisclosed set-delayed cement compositions may also directly orindirectly affect the various downhole equipment and tools that may comeinto contact with the set-delayed cement compositions such as, but notlimited to, wellbore casing, wellbore liner, completion string, insertstrings, drill string, coiled tubing, slickline, wireline, drill pipe,drill collars, mud motors, downhole motors and/or pumps, cement pumps,surface-mounted motors and/or pumps, centralizers, turbolizers,scratchers, floats (e.g., shoes, collars, valves, etc.), logging toolsand related telemetry equipment, actuators (e.g., electromechanicaldevices, hydromechanical devices, etc.), sliding sleeves, productionsleeves, plugs, screens, filters, flow control devices (e.g., inflowcontrol devices, autonomous inflow control devices, outflow controldevices, etc.), couplings (e.g., electro-hydraulic wet connect, dryconnect, inductive coupler, etc.), control lines (e.g., electrical,fiber optic, hydraulic, etc.), surveillance lines, drill bits andreamers, sensors or distributed sensors, downhole heat exchangers,valves and corresponding actuation devices, tool seals, packers, cementplugs, bridge plugs, and other wellbore isolation devices, orcomponents, and the like.

EXAMPLES

To facilitate a better understanding of the present embodiments, thefollowing examples of certain aspects of some embodiments are given. Inno way should the following examples be read to limit, or define, thescope of the embodiments.

Example 1

A sample set-delayed cement composition was prepared with the followingcomponents: pumice (DS-325 lightweight aggregate), hydrated lime,dispersant (Liquimee 5581F), primary retarder (Micro Matrix® cementretarder), weighting additive (MicroMax® Weight Additive, available fromHalliburton Energy Services, Inc., Houston, Tex.), secondary retarder(HR®-5 cement retarder, available from Halliburton Energy Services,Inc., Houston, Tex.), Class H Portland cement, and water. Eachcomponent, with the exception of the primary retarder (Micro Matrix®cement retarder), is presented as a percentage of the weight of pumice(bwoP). The primary retarder is measured in units of gallons per 46pound sack of pumice (gal/sk). The compositional makeup is listed inTable 1 below.

TABLE 1 Sample Set-Delayed Cement Compositional Makeup Material AmountUnits Weight (g) % bw in total Pumice 100 % bwoP 58682.7 55.56 Hydratedlime 20 % bwoP 11736.5 11.11 Dispersant 0.5 % bwoP 291.1 0.28 PrimaryRetarder 0.06 gal/sk 734.6 0.70 Weighting Additive 2 % bwoP 1173.7 1.11Secondary Retarder 0.5 % bwoP 293.4 0.28 Portland Cement 2 % bwoP 1173.71.11 Water 53.7 % bwoP 31534.5 29.86 Total — — 105620.2 100

The sample in Example 1 remained fluid, mixable, pumpable, and stablewith no solids settling or gelation for greater than 40 days. The samplehad a measured density of 13.5 pounds per gallon. Minimal doses ofdispersant were added during the storage period to maintain the slurry'soptimal rheology. This exemplary sample serves as the base slurry forthe remaining examples provided below.

Example 2

The rheological properties of the sample set-delayed cement compositionof Example 1 were measured after storing the samples at room temperatureand pressure for a period of 41 days. After preparation, the rheologicalproperties of the samples were determined using a Model 35A FannViscometer and a No. 2 spring with a Fann Yield Stress Adapter, inaccordance with the procedure set forth in API RP Practice 10B-2,Recommended Practice for Testing Well Cements. The results of this testare set forth in Table 2 below.

TABLE 2 Viscosity Tests Age of Sample FYSA Readings (days) RPM 3 6 100200 300 3D 6D 41 AVG. 13 13 35 56 75.5 5 4

Example 3

Three sample set-delayed cement compositions, samples 1-3, and twocontrols, controls 1 and 2, were prepared from the base slurry describedin Example 1. Foamer 1026™, a foaming additive, was added to each of thethree samples in varying amounts after a time period of 41 days.Additionally, a cement set activator. CaCl₂, was added to sample 2 andcontrol 2. The amount of the cement set activator added to each samplewas sufficient to deliver a 5% by weight of pumice activator amount tothe set-delayed cement composition. The base and foamed densities weremeasured. Additionally, the destructive compressive strength wasmeasured using a mechanical press in accordance with API RP Practice10B-2, Recommended Practice far Testing Well Cements. Additionally, thedestructive compressive strength was measured by allowing the samples tocure in a 2″ by 4″ plastic cylinder that was placed in a water bath at190° F. to form set cylinders. Immediately after removal from the waterbath, destructive compressive strengths were determined using amechanical press in accordance with API RP 10B-2, Recommended Practicefor Testing Well Cements. The results of this test are set forth below.The reported compressive strengths are an average for two cylinders ofeach sample. The samples and controls were cured at 1 atmosphere, 190°F.; compressive strength measurements were taken at 72 hours.

TABLE 3 Compositional Makeup and Characteristics Sample 1 Sample 2Sample 3 Control 1 Control 2 Sample 1363.2 1363.2 1363.2 817.5 817.5Weight (g) Foaming 8.14 12.21 14 — — Additive (g) Activator (g) — 37.87— — 25.8 Base Density 13.5 13.5 13.5 13.5 13.3* (ppg) Foamed 11 9.1 9.2— — Density (ppg) Foam 19% 33% 32% — — Quality Compressive 639.37 534.45135.18 1222.46 1360.14 Strength (psi) *Density of Control 2 with theActivator.

In addition to the characteristics of Table 3, the foam stability ofsamples 1-3 was measured in both the slurry state and the set state.This data is set forth in Table 4 below.

TABLE 4 Foam Stability Measurements. Foam Stability Sample 1 Sample 2Sample 3 Slurry Set Slurry Set Slurry Set More than a trace of freefluid? N N N N N N Bubbles on surface of bubble coalescing N N N N N N(breaking, enlargement, merging)? Excessive column-height reduction? N NN N N N Signs of density segregation (streaking or dark N N N N N Ncoloration from top to bottom)?

The Archimedes Method was used to measure the slurry density of Samples1-3 in top, middle, and bottom portions. Densities that were close inweight from top to bottom indicate stable foam while considerablevariation in densities indicates unstable foam. All units are in poundsper gallon. This data is set forth in Table 5 below.

TABLE 5 Density Uniformity Archimedes Method Example 1 Example 2 Example3 Top (ppg) 10.50 8.95 9.26 Middle (ppg) 10.52 8.99 9.30 Bottom (ppg)10.46 8.83 9.25

Lastly, the rheology of foamed Samples 1-3 was measured using the sametechnique as used in Example 2 to measure the rheology of the baseslurry. The base slurry is designated as Control 1 in Table 6 below. Therheology data is set forth in Table 6 below.

TABLE 6 Viscosity Tests Density FYSA Readings (ppg) RPM 3 6 100 200 3003D 6D Control 1 13.5 AVG. 13 13 35 56 75.5 5 4 Sample 1 11 AVG. 10 10.533.5 50.25 65.5 3.5 2.5 Sample 2 9.1 AVG. 2.25 3 17.5 29.5 40 1.5 1Sample 3 9.2 AVG. 17 17.5 40.5 56.5 70.5 12 9

Example 3 thus indicates that the foamed slurries exhibit goodcompressive strength while maintaining suitable rheologies and uniformdensities.

Example 4

Two sample set-delayed cement compositions, samples 4 and 5, wereprepared from the base slurry described in Example 1. A cement setactivator, CaCl₂, was added to the samples in an amount sufficient todeliver a 5% by weight of pumice activator amount to the set-delayedcement composition. Sample 5 further included graphitic carbon fibers inan amount of about 0.18% by weight of the pumice. The graphitic carbonfibers were PAN carbon fibers derived from polyacrylonitrile. Foamer1026™, a foaming additive, was added to each of the samples in an amountof 0.18% by weight of the pumice. Additionally, the destructivecompressive strength was measured by allowing the samples to cure in a2″ by 4″ plastic cylinder that was placed in a water bath at 190° F. toform set cylinders. Immediately after removal from the water bath,destructive compressive strengths were determined using a mechanicalpress in accordance with API RP 10B-2, Recommended Practice for TestingWell Cements. The results of this test are set forth below. The reportedcompressive strengths are an average for three cylinders of each sample.The samples and controls were cured at 1 atmosphere, 190° F.:compressive strength measurements were taken at 72 hours.

TABLE 7 Compositional Makeup and Characteristics Sample 4 Sample 5 BaseSlurry (g) 1000 1000 Carbon Fiber (g) — 10 Activator (g) 27.8 27.8Foaming Additive (g) 10 10 Base Density (ppg) 13.5 13.5 Foamed Density(ppg) 8.33 8.33 Compressive Strength (psi) 62 143

It should be understood that the compositions and methods are describedin terms of “comprising,” “containing,” or “including” variouscomponents or steps, the compositions and methods can also “consistessentially of” or “consist of” the various components and steps.Moreover, the indefinite articles “a” or “an,” as used in the claims,are defined herein to mean one or more than one of the element that itintroduces.

For the sake of brevity, only certain ranges are explicitly disclosedherein. However, ranges from any lower limit may be combined with anyupper limit to recite a range not explicitly recited, as well as, rangesfrom any lower limit may be combined with any other lower limit torecite a range not explicitly recited, in the same way, ranges from anyupper limit may be combined with any other upper limit to recite a rangenot explicitly recited. Additionally, whenever a numerical range with alower limit and an upper limit is disclosed, any number and any includedrange falling within the range are specifically disclosed. Inparticular, every range of values (of the form, “from about a to aboutb,” or, equivalently. “from approximately a to b,” or, equivalently,“from approximately a-b”) disclosed herein is to be understood to setforth every number and range encompassed within the broader range ofvalues even if not explicitly recited. Thus, every point or individualvalue may serve as its own lower or upper limit combined with any otherpoint or individual value or any other lower or upper limit, to recite arange not explicitly recited.

Therefore, the present embodiments are well adapted to attain the endsand advantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, and may bemodified and practiced in different but equivalent manners apparent tothose skilled in the art having the benefit of the teachings herein.Although individual embodiments are discussed, the invention covers allcombinations of all those embodiments. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. Also, the terms in the claimshave their plain, ordinary meaning unless otherwise explicitly andclearly defined by the patentee. It is therefore evident that theparticular illustrative embodiments disclosed above may be altered ormodified and all such variations are considered within the scope andspirit of the invention. If there is any conflict in the usages of aword or term in this specification and one or more patent(s) or otherdocuments that may be incorporated herein by reference, the definitionsthat are consistent with this specification should be adopted.

What is claimed is:
 1. A foamed set-delayed cement compositioncomprising: water, pumice, hydrated lime, a foaming additive, entrainedgas, and a set retarder.
 2. The composition of claim 1 wherein thefoaming additive is selected from the group consisting of: a betaine;hydrolyzed keratin; an amine oxides; an alkyl or alkene dimethyl amineoxide; a cocoamidopropyl dimethyl amine oxide; a methyl ester sulfonate;an alkyl or alkene dimethyl amidobetaine; cocoamidopropyl betaine; analpha-olefin sulfonate; a quaternary surfactant; trimethyltallowammoniumchloride; trimethylcocoammonium chloride; a C8 to C22 alkylethoxylatesulfate; and any combination thereof.
 3. The composition of claim 1wherein the foamed set-delayed cement composition has a foam qualitybetween about 5% to about 80%.
 4. The composition of claim 1 wherein thefoamed set-delayed cement composition has a density between about 9pounds per gallon to about 11 pounds per gallon.
 5. The composition ofclaim 1 wherein the set retarder comprises at least one retarderselected from the group consisting of a phosphonic acid, a phosphonicacid derivative, a lignosulfonate, a salt, an organic acid, a cellulosederivate, a synthetic co- or ter-polymer comprising sulfonate andcarboxylic acid groups, a borate compound, and any combination thereof.6. The composition of claim 1 wherein the foamed set-delayed cementcomposition further comprises a dispersant, and wherein the dispersantcomprises at least one dispersant selected from the group consisting ofa sulfonated-formaldehyde-based dispersant, a polycarboxylated etherdispersant, and a combination thereof.
 7. The composition of claim 1wherein the foamed set-delayed cement composition further comprises acement set activator, and wherein the cement set activator comprises atleast one activator selected from the group consisting of an amine, asilicate, zinc formate, calcium acetate, a Group IA hydroxide; a GroupIIA hydroxide, a monovalent salt, a divalent salt, nanosilica, apolyphosphate, and any combination thereof.
 8. The composition of claim1 wherein the foamed set-delayed cement composition remains in apumpable state for at least about one day to about one week.
 9. Thecomposition of claim 1 wherein the pumice has a particle size of about 1micron to about 200 microns.
 10. The composition of claim 1 wherein thehydrated lime is present in an amount of about 10% to about 100% byweight of the pumice.
 11. The composition of claim 1 wherein foamed setdelayed cement composition further comprises a set retarder is presentin an amount of about 0.01% to about 10% by weight of the pumice. 12.The composition of claim 1 wherein foamed set delayed cement compositionfurther comprises a dispersant is present in an amount of about 0.01% toabout 5% by weight of the pumice.
 13. The composition of claim 1 whereinfoamed set delayed cement composition further comprises a cement setactivator is present in an amount of about 1% to about 20% by weight ofthe pumice.
 14. The composition of claim 1 wherein the set-delayedcement composition further comprising at least one mechanical propertyenhancing additive selected from the group consisting of graphiticcarbon fibers, glass fibers, steel fibers, mineral fibers, silicafibers, polyester fibers, polyamide fibers, and polyolefin fibers, andany combinations thereof.
 15. The composition of claim 14 wherein themechanical property enhancing additive is present in an amount fromabout 0.01% to about 5% by weight of the pumice.
 16. The composition ofclaim 1 wherein the set-delayed cement composition develops a 24-hourcompressive strength of about 500 psi to about 2400 psi.
 17. A foamedset-delayed cement composition comprising: water, pumice, hydrated lime,a foaming additive, entrained gas, Portland cement, and a set retarderwherein the set retarder comprises a primary retarder and a secondaryretarder.
 18. The composition of claim 17 wherein the set retardercomprises at least one retarder selected from the group consisting of aphosphonic acid, a phosphonic acid derivative, a lignosulfonate, a salt,an organic acid, a cellulose derivate, a synthetic co- or ter-polymercomprising sulfonate and carboxylic acid groups, a borate compound, andany combination thereof.
 19. The composition of claim 17 wherein thefoamed set-delayed cement composition further comprises a dispersant,and wherein the dispersant comprises at least one dispersant selectedfrom the group consisting of a sulfonated-formaldehyde-based dispersant,a polycarboxylated ether dispersant, and a combination thereof.
 20. Thecomposition of claim 17 wherein the foamed set-delayed cementcomposition further comprises a cement set activator, and wherein thecement set activator comprises at least one activator selected from thegroup consisting of an amine, a silicate, zinc formate, calcium acetate,a Group IA hydroxide; a Group IIA hydroxide, a monovalent salt, adivalent salt, nanosilica, a polyphosphate, and any combination thereof.